Trailers including expandable sides are well known in the art. The expandable trailers are used as medical coaches for, for example, mobile medical or dental offices, mobile surgical hospitals, and disaster response centers. The expandable trailers may also be used for educational centers such as bookmobiles, children's labs, and police/fire trainers, for canteen units, bloodmobiles, and other uses which require expansive floor space for equipment or inventory in a mobile unit.
The expanding sides of the trailer provide an enlarged floor space on a standard trailer without increasing the transportation width or length. When the portable trailer is moved to the desired location, the expandable sides extend perpendicularly from the sides of the trailer to provide additional floor space within the interior of the trailer.
Prior art trailers include a non-inflatable, lip-type seal mounted on either the expandable section, the trailer opening perimeter, or a combination of both. If the sides of the expandable section are not exactly square with the body of the prior art trailer, the seal will not fully close the gap between the walls of the expandable section and the sides of the trailer, leaving openings for water, dust, air and snow to pass through. Prior art trailers, therefore, require a high working precision between the sides of the expandable section and the exterior surface of the trailer to prevent the expandable sections from leaking or otherwise exposing the interior of the trailer to adverse environmental elements. The propensity of the prior trailers to expose the interior of the trailer to the environmental elements was caused by the inability of the prior art trailers to effectively and inexpensively seal the gap between the sides of the expandable sections and the body of the trailer.
Expandable sections on prior art trailers were extended and retracted using ordinary rack and pinion sliding mechanisms on each of the four sides of the expandable sections. Gear assemblies, mounted on the frame of the trailer, coordinated with corresponding gear racks on each of the sides of the expandable sections. Each rack and pinion sliding mechanism was then motor controlled to automatically extend and retract the expandable sections during working and transporting modes, respectively. Unfortunately, each rack and pinion mechanism required precise alignment with every other rack and pinion mechanism on the expandable section to insure the smooth and uniform extending and retracting operations of the expandable section. Even minute misalignment between any of the rack and pinion mechanisms, caused by a foreign object in any individual gear assembly or by imprecise miter box controllers for the system of gear assemblies, resulted in, at best, an uneven gap in the expandable section and, at worst, a completely bound and inoperable expandable section.
But, because of the slidable nature of the expandable section within the body of the trailer, some gap, however small, between the sides of the expandable section and the body of the trailer, was required to allow the expandable section to move within the opening. Even though a narrow gap was difficult and expensive to obtain with prior art designs, certain trailers required an extremely low gap tolerance, such as medical and dental trailers, in which sterile environments were desired. In these applications, and others which require an environmentally protected trailer interior, the prior art trailers were required to maintain a precisely aligned opening by careful and close control over the driving alignment between each of the rack and pinion sliding mechanisms and the miter boxes distributing the power from the gear motors to the individual gear assemblies to insure that the seal was effectively aligned within the trailer opening. The difficulty of precisely controlling each of the rack and pinion sliding mechanisms and the miter boxes driving the sliding mechanisms dictated that perfect alignment between the expandable section and the body of the prior art trailer was impossible and, even extremely close alignment was extremely expensive to acquire.
Due to the inability of trailer manufacturers to provide an inexpensive, expandable section for a trailer which effectively sealed the interior of the trailer from the environmental elements, expandable trailers were generally inappropriate or unfeasibly costly for sterile or super-clean applications.
The prior art trailer further lacked adequate environmental protection by requiring those using the expandable trailers to take the extra precautions to sweep off snow, water and dust from the top of the expandable section before retracting the section into the body of the trailer, to prevent the elements from riding into the trailer on top of the expandable section during retraction. Again, complete environmental protection, including reducing the amount of accumulated snow, water and dirt which entered the trailer during retraction of the expandable section, could only be achieved by a precise working alignment between the walls of the expandable section and the body of the trailer since only a precisely aligned expandable section would push the accumulated elements from the top surface of the expandable section during retraction.
Even a precisely manufactured prior art trailer, having a narrowly constructed gap immediately after manufacture, was susceptible to the effects of transit shock on the gap alignment. Torsional forces exerted on the expandable section within the trailer body during transit would degrade the "squareness" of the expandable section within the body of the trailer to further encourage misalignment between the rack and pinion sliding mechanisms. Consequently, investing the expense to manufacture an expandable trailer to accommodate low tolerance applications was impractical since the trailer was quickly misaligned by the wear of transportation. An expandable trailer section is needed which simply and inexpensively secures the expandable section against the effects of transit shock to substantially eliminate misalignment associated with transit.
Prior art trailers were also unable to seal hot and cold air drafts from the interior, expanded trailer space rising from the temporary floor panels within the expanded section. Prior art trailers used multiple floor panels, either completely removable or foldable on hinges, to be removed or raised while the expandable section was retracted and lowered while the expandable section was extended. The floor panels were laid end to end within the expanded interior space of the trailer to create a level floor and were generally ineffective in sealing the gaps created between the respectively lowered floor panels. Buckling, warping, splitting and cracking in the multiple floor panels contributed to the misalignment of the floor panels when they were lowered to the floor level, permitting hot and cold air drafts to rise from the floor through the gaps created by the misaligned panels. An expandable trailer is needed which effectively seals the interior of the expandable section from air drafts raising from the floor of the expandable section.
In summary, for applications in which the extra floor space provided by an expandable trailer would be desirable, the expense and complications associated with obtaining a well-aligned and well-sealed trailer was generally prohibitive. A mobile trailer, having expandable sections to increase the interior floor space, is needed in which the expandable sections simply, cheaply and effectively protect the interior of the trailer from the various adverse environmental elements.